On the -R/+R question, the answer is "it depends." It depends on the set-top DVD players that your clients have. Neither flavor will be guaranteed to work in 100% of the players out in client-land. (Actually, no "burned" DVD can be guaranteed to work on 100% of the players.) You might have to do another version, if you get complaints/returns. Still, with each passing year, the flavor of DVD media seems to mean less. Do follow Harm's suggestion on media brand though, and burn as slowly, as you can. Encore can be set for some pretty slow burn speeds, dependant on your media and your burner. Go with the lowest speed that it allows. A moment saved by burning fast will likely come back to haunt you with some clients' players. It takes less time to do it slowly now, than to have to do a re-burn later. Just get a cup of coffee, while you burn at 2x, or whatever.

I use Falcon DVD-R media (only available in the US from DiskMakers) with an AD-7200S burner, and even burning at 18X I routinely create disks with fewer playback errors than the disks Hollywood makes. Not a one has ever failed to play for a client.

Verbatims I got no idea, in the begining when Cds came out to
the market, I bough a few and put it trough test, I mean dropping
hot water on it, and things like that, most loss the cover
leaving you only the transparent plastic, at that time
the only one that resisted was Memorex, however I had been
seening a few errors here and there on videos that I make and I wonder
if quality of current Memorex is the problem.
I will try one of those brands.............

As far as I know (based on reading in various Premiere forums) Memorex does not make their own discs... they buy from "various" places, which means you may get good ones, or crap... sometimes in the same bundle so you get a good burn and the next disc doesn't work well